Use new Skia .gni file for sources, remove .gypis.

skia/skia_pdfium.gypi

-# Copyright 2013 The Chromium Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
-
-
-# This gypi file contains all the PDFium-specific enhancements to Skia.
-# In component mode (shared_lib) it is folded into a single shared library with
-# the Skia files but in all other cases it is a separate library.
-{
-  'dependencies': [
-    'skia_library',
-  ],
-
-  'direct_dependent_settings': {
-    'include_dirs': [
-      'ext',
-    ],
-  },
-  'variables': {
-    # TODO(scottmg): http://crbug.com/177306
-    'clang_warning_flags_unset': [
-      # Don't warn about string->bool used in asserts.
-      '-Wstring-conversion',
-    ],
-  },
-  'sources': [
-    'config/SkUserConfig.h',
-    'ext/google_logging.cc',
-  ],
-}